Various mechanisms have been devised to steer vehicles such as motorcycles, snowmobiles, ATVs, mopeds, scooters, bicycles, and other similar apparatus. One such steering mechanism involves a handlebar connected to a fork, which, in turn, is connected to the axle and wheel of a motorcycle or the ski of a snowmobile. The fork rotates about an axis generally perpendicular to the riding surface. Turning the handlebar rotates the fork and pivots the wheel to the desired direction.
Typically, a unitary handlebar is connected to the steering head or triple clamp (tree) of a fork by connecting means such as clamps. Such assemblies may come in a variety of fixed heights, widths, lengths, and angles to accommodate riders of varying sizes and riding styles.
There have been several attempts at multi-adjustable handlebars. Equipped with such a handlebar, a vehicle can accommodate riders of differing heights, arm lengths, etc. Additionally, the same individual may adjust the handlebar to improve aerodynamics or to enhance riding comfort.
However, it is apparent that some adjustable handlebar designs suffer from certain disadvantages as to practicality, safety, or weight considerations. For example, U.S. Pat. No. 4,361,057 discloses a single-pivot drop-style bicycle handlebar adjustable between a downward or racing position and an upward position for touring or general use. A disadvantage of such a limited, single-axis, pivotal mounting systems is that the handlebars experience substantial rotation about a horizontal axis as they are adjusted up, down, front or back. As a result, the handlebars are moved out of a desired orientation into an inconvenient and uncomfortable orientation. Also, gauges, controls and the like mounted on the handlebars may be rotated out of their initial positions.
In addition, safety features were not typically considered in prior designs. Safe vehicle performance is especially important in motorcycle operation. Few other activities expose a (mostly) unprotected operator to streams of traffic including multi-ton vehicles traveling over 60 miles per hour. Safety can be divided into two categories, normal operational performance and degraded performance. Normal operational performance considers the controllability of the vehicle during normal operation. Degraded performance considers vehicle controllability in an abnormal situation. Each should be considered in a handlebar assembly design.
Considering safety during normal operational performance, previous adjustable handlebar assemblies could flex excessively due to weight-saving designs. While excessive weight is a concern, excessive flex is notably relevant to safety. U.S. Pat. No. 4,023,436 discloses unbraced rotating tubular projections independently supporting handgrips at their extremities. Avoiding flex is important because motorcycles are steered through handlebar rotation. Body lean also determines the direction of travel, and complicating this is countersteering that is required to initiate a turn. In countersteering, the fork must first be briefly turned in the direction opposite the turn to initiate it. It is then turned back to the direction of the turn. This rapid back and forth rotation can result in oscillations if the tire/fork/riser/handlebar assembly flexes excessively. Included with this are the gyroscopic forces of the front wheel that must be overcome. Flex-resistance needs to be a consideration of any safe handlebar assembly, and lightweight and flex-resistance are features for safety and performance.
Safety with respect to degraded performance considers vehicle controllability in an abnormal situation. Previous adjustable handlebar assemblies typically exhibited single point failure modes. If one bolt or attaching screw loosened or broke, the result would be a catastrophic joint failure. Additionally, existing designs included protruding surfaces that are not only a safety concern but also aesthetically unappealing. Related to this is the effect of a loosened, not failed, joint of an adjustable handlebar. Without a feature such as a stop to limit movement, a loosened joint may rotate 360 degrees, resulting in uncontrollability. Stops can typically provide enough control to safely stop a hampered vehicle.
Furthermore, the adjustability of the handlebar also impacts the safety as normal handlebars are designed for a certain height and arm length. Those that are outside of the design criteria, particularly women, may not be in the ideal position for operation.
What is needed, therefore, is an adjustable handlebar system that alleviates or diminishes the problems noted in the state of the art and provides a safe assembly that allows for user adjustability. Such a system should be aesthetically pleasing and accommodate adjustments in multiple axes to satisfy the user requirements.